Grinder pressing device

ABSTRACT

A grinder pressing device, wherein either the bottom part of a cylinder main body ( 10 ) of an air cylinder ( 1 ) in a vertical posture or a piston rod ( 11 ) is fixed to a fixed plate ( 2 ) and the other one is fixed to a movable plate ( 3 ) disposed under the fixed plate ( 2 ), either a guide table (G 2 ) or a guide (G 1 ) is mounted on the movable table ( 3 ) and the other one is mounted on the outer peripheral surface of the cylinder main body ( 20 ) and the guide plate (G 2 ) is guided on the guide (G 1 ) in a vertical direction under the rolling frictional condition through balls and, in the air cylinder ( 1 ), a coefficient of friction between the outer peripheral walls of a piston ( 12 ) and the piston rod ( 11 ) and the structural wall of the cylinder main body ( 10 ) is set lower by a metal seal so as to support the piston rod ( 11 ) by a ball bush movably in forward and backward directions over an extensive distance, a grinder (G) being mounted on the movable plate ( 3 ) and air pressures in upper and lower cylinder chambers ( 13  and  14 ) divided by the piston ( 12 ) being controlled so as to adjust the pressing force of the grinder (G) to a work to be ground.

FIELD OF THE INVENTION

The present invention relates to a grinder pressing device.

DESCRIPTION OF THE RELATED ART

Pressing force applied to an object to be ground by a grinderconsiderably affects grinding performance, grinding accuracy, life ofthe grindstone, and the like, and therefore grinding operation by arobot is carried out so as to maintain pressing force predetermined byvarious means.

There are types of grinder device; an electric grinder and an airgrinder. In the former grinder, pressing force is controlled by aservomotor by determining pressing force applied to the object by agrindstone according to current of a grinder motor. In the lattergrinder, pressing force is controlled by giving a command to a robot byusing a six-axis sensor, for example.

However, in such controlling methods of pressing force, both the devicesper se are expensive and, especially in the method of giving the commandto the robot by using the six-axis sensor, control is complicated.

It is hence an object of the present invention to provide a grinderpressing device which is, irrespective of types of grinder, inexpensiveand capable of compensating wear of a grindstone and/or a slightdisplacement of an object to be ground.

SUMMARY OF THE INVENTION

In a grinder pressing device according to the present invention, one ofa bottom portion of a cylinder main body and a piston rod of an aircylinder in a vertical posture is attached to a fixed plate and theother is attached to a movable plate disposed below the fixed plate, oneof a guide table and a guide is mounted on a movable plate side and theother is mounted on an outer peripheral face of the cylinder main body.The guide table is guided on the guide in a vertical direction under therolling frictional condition through balls. In the air cylinder,hermeticity between outer peripheral walls of a piston and the pistonrod and a structural wall of the cylinder main body side is provided bymetal seals and friction coefficients between the walls is set low, andthe piston rod is supported by a ball bushing in a large area so as tobe movable forward and backward. A grinder is mounted to the movableplate directly or through another member, and pressing force of thegrinder to an object to be ground can be controlled by adjusting airpressure of upper and lower cylinder chambers separated by the piston.

Moreover, a grinder pressing device of the present invention includes ahanging member having a grinder mounting portion and a partition plate,upper and lower bellows cylinders fixedly disposed on upper and lowerfaces of the partition plate, and a retaining member for maintaining aconstant distance between an upper face of the upper bellows cylinderand a lower face of the lower bellows cylinder. The grinder pressingdevice is used in a manner that the retaining member is fixed to a fixedportion F or a robot output portion, that a grinder is provided on thegrinder mounting portion, and that the upper and lower bellows cylindersare supplied with air of respectively predetermined pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view showing an air circuit of a grindingsystem using a grinder pressing device in Embodiment 1 of the presentinvention.

FIG. 2 is a front view of a grinder, the grinder pressing device and thelike forming the grinding system.

FIG. 3 is a front view in which a piston rod of an air cylinder in thegrinder pressing device is put in a contracted state from the stateshown in FIG. 2.

FIG. 4 is a side view of the grinder pressing device.

FIG. 5 is a sectional view taken along a line V—V in FIG. 3.

FIG. 6 is an explanatory view of the air cylinder in the grinderpressing device.

FIG. 7 is a partially sectional perspective view of a device formed bycombining a guide and a guide table used for the grinder pressingdevice.

FIG. 8 is a sectional view of the device formed by combining the guideand the guide table taken along line VIII—VIII in FIG. 7.

FIG. 9 is an explanatory view showing an air circuit of a grindingsystem using a grinder pressing device in Embodiment 2 according to thepresent invention.

FIG. 10 is a front view of the grinder, the grinder pressing device andthe like forming the grinding system in Embodiment 2 of presentinvention.

FIG. 11 is a side view of the grinder, the grinder pressing device andthe like forming the grinding system in Embodiment 2 of presentinvention.

PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

The present invention is described in detail in conjunction with theaccompanying drawings.

[Embodiment 1]

As shown in FIG. 1, the grinding system of this embodiment includes agrinder pressing device GK for supporting a grinder G and a compressor Cfor driving the grinder G to rotate and sending air to the grinderpressing device GK. Selector valves K1, K2, electro-pneumaticproportional valves K3, K4, and pressure sensors P1, P2 are provided toair lines connecting the compressor C and the grinder G or the grinderpressing device GK.

Main structural portions of this grinding system will be describedbelow.

The grinder G shown in FIG. 1 is an air-type grinder in which agrindstone g is driven to rotate by compressed air from the compressor Cand compressed air is fed through the above selector valve K2.

In the grinder pressing device GK, as shown in FIGS. 2 and 3, a bottomportion of a cylinder main body 10 of an air cylinder 1 in a verticalposture is fixed to a fixed plate 2, and a movable plate 3 is attachedto an end portion of a piston rod 11 of the air cylinder 1. A guidetable G2 is mounted to the movable plate 3 side, and a guide G1 ismounted on an outer peripheral face of the cylinder main body 10. Asshown in FIGS. 7 and 8, the guide table G2 is guided on the guide G1 ina vertical direction under the rolling frictional condition throughballs B (steel balls). As shown in FIGS. 3 to 5, the grinder pressingdevice GK has a linear sensor RS for detecting a position of the movableplate 3 with respect to the fixed plate 2 so that a position of thegrinder G can be detected, and further a dust-proof bellows pipe 4surrounding parts and members present between the fixed plate 2 and themovable plate 3. As shown in FIGS. 2 and 6, by adjusting air pressuresin upper and lower cylinder chambers 13 and 14 separated by a piston 12,pressing force applied to an object to be ground by the grindstone g ofthe grinder G fixed to the movable plate 3 through a mounting plate 49can be adjusted.

As shown in FIG. 6, the air cylinder 1 is basically formed with thecylinder main body 10, the piston 12 for dividing an inside of thecylinder main body 10 into the cylinder chambers 13 and 14, and thepiston rod 11 connected to the piston 12. Supply and discharge of air toand from the cylinder chambers 13 and 14 cause the piston 12 to move tochange a projecting portion of the piston rod 11 from the cylinder mainbody 10. In this Embodiment, as shown in FIG. 6, the cylinder main body10 is formed by combining members 10 a to 10 h and the like, and O-ringsOR are disposed between the members where hermeticity is required.

In this air cylinder 1, as shown in FIG. 6, airtightness is provided bymetal seals MS between an outer peripheral wall of the piston 12 and aninner peripheral wall of the member 10 d and between an outer peripheralwall of the piston rod 11 and an inner peripheral wall of the member 10h so as to set friction coefficients between the walls low. The pistonrod 11 is supported by a ball bushing BS in a large area of the pistonrod 11 so that the piston rod 11 can move forward and backward.Reference numeral 19 in FIG. 6 denotes a grease groove.

The fixed plate 2 has two air lines 20 and 21 extending from a side faceto a lower face of the fixed plate 2 as shown in FIGS. 2 and 3 and isattached to the fixed portion F through another member as shown in FIG.1.

As shown in FIGS. 1 and 2, air that has passed through theelectro-pneumatic proportional valve K3 is supplied to the cylinderchamber 14 through the air line 20 and a tube Tl, while air that haspassed through the electro-pneumatic proportional valve K4 is suppliedto the cylinder chamber 13 through the air line 21 and a tube T2.

The movable plate 3 and the mounting plate 49 are united with each otherwith a bolt and the like, and, as shown in FIG. 2, the grinder G isattached to the mounting plate 49 in a manner that a posture of thegrinder G can be changeable.

The bellows pipe 4 is made of rubber material and, as shown in FIG. 2,core wires are embedded in outer peripheral sharp portions 40 so thatthe bellows pipe 4 has very small expansion-contraction resistance andshape retention in a diameter direction. A part of the bellows pipe 4 inthis Embodiment takes the form of mesh through which air can come intoand go out of the bellows pipe 4.

The guide G1 and the guide table G2 are assembled with each otherthrough balls B as shown in FIGS. 7 and 8. When the guide table G2 moveson the guide G1, the balls rotatively circulate. The balls B haveangular-contact structure of 45° with respect to the guide G1 and areapplied with well-balanced preload. Therefore, the balls B have the samerated load in vertical and horizontal directions and maintain aconstantly low coefficient of rolling friction.

As shown in FIGS. 2 and 3, the guide G1 is mounted on an outer face ofthe cylinder main body 10 of the air cylinder 1 in a vertical postureand the guide table G2 is mounted on a bracket 39 erectly provided onthe movable plate 3. A range of movement of the guide table G2 withrespect to the guide G1 is determined by upper-limit and lower-limitstoppers.

The linear sensor RS detects a position of the movable plate 3 withrespect to the fixed plate 2 in order to detect a position of thegrinder G, as described above. As shown in FIGS. 4 and 5, the linearsensor RS is disposed in a manner that a main body RS1 thereof ismounted to the cylinder main body 10 and a rod RS2 thereof is mounted onthe movable plate 3. The rod RS2 of the linear sensor RS is movable withsmall resistance to the main body RS1.

With the structure of the grinder pressing device GK as stated above,air pressure to the cylinder chambers 13 and 14 can be adjusted bychanging voltage or current to the electro-pneumatic proportional valvesK3 and K4. As a result, the pressing force of the grindstone g to theobject to be ground can be set at a desired value.

In the air cylinder 1 used for the grinder pressing device GK, frictioncoefficients between the outer peripheral wall of the piston 12 and theinner peripheral wall of the member 10 d and between the outerperipheral wall of the piston rod 11 and the inner peripheral wall ofthe member 10 h are respectively set low, and the piston rod 11 issupported by a ball bushing BS in a large area of the piston rod 11 sothat the piston rod 11 can move forward and backward. Therefore, thepressing force of the grindstone g to the object to be ground can becompensated irrespective of wear of the grindstone g or a slightdisplacement of the object to be ground.

Furthermore, use of the grinder pressing device GK eliminates anexpensive device and enables very easy control, thereby cost beinglowered.

In this Embodiment 1, design modifications of the following (1) to (6)may be made.

(1) In the above Embodiment, the vertical movement of the grinder G andthe pressing force of the grindstone g to to the object to be ground areset by changing internal pressures in the cylinder chambers 13 and 14 ofthe air cylinder 1 by using the two electro-pneumatic proportionalvalves K3 and K4. Alternatively, air pressure fed to one of the cylinderchambers 13 and 14 is fixed while air pressure fed to the other isvariable.

(2) In a system in which the grindstone g presses the object to beground while the object being moved vertically, both of the airpressures fed to the cylinder chambers 13 and 14 of the air cylinder 1may be fixed.

(3) The grinder G used in the system of the above Embodiment is an airtype one. However, an electric grinder may be selectively employed inthe system.

(4) The grinder G is, although not limited thereto, attached to thefixed portion F through the grinder pressing device GK in the system ofthe above Embodiment. Optionally, for example, the grinder G may beattached to an output portion of a robot through the grinder pressingdevice GK.

(5) Different from the above Embodiment, the end portion of the pistonrod 11 of the air cylinder 1 in the vertical posture may be fixed to thefixed plate 2 and a bottom portion of the cylinder main body 10 may bemounted on the movable plate 3 to form the grinder pressing device GK.

(6) Different from the above Embodiment, the guide G1 may be attached tothe movable plate 3 side and the guide table G2 may be mounted on theouter peripheral face of the cylinder main body 10.

[Embodiment 2]

The grinding system in this Embodiment, as shown in FIG. 9, includes agrinder G, a grinder pressing device GK for supporting the grinder G, acompressor C for driving the grinder G to rotate and feeding air to thegrinder pressing device GK, and further as shown in FIG. 10, a frame 99(corresponding to the fixed portion F) for supporting the grinderpressing device GK. Selector valves K1 and K2, electro-pneumaticproportional valves K3 and K4, and pressure sensors P1 and P2 areprovided to air lines connecting the compressor C and the grinder G orthe grinder pressing device GK.

Main structural portions of the grinding system will be described below.

As shown in FIG. 9, an air-type grinder in which compressed air from thecompressor C drives a grindstone g to rotate is employed as the grinderG. The compressed air is fed through the above selector valve K2.

As shown in FIGS. 10 and 11, the grinder pressing device GK has ahanging member 5 on which the grinder G is hung, upper and lower bellowscylinders 6 and 7 fixedly disposed on upper and lower faces of apartition plate 51 of the hanging member 5 that will be described later,a retaining member 8 for maintaining a constant distance between anupper face of the upper bellows cylinder 3 and a lower face of the lowerbellows cylinder 7, a linear sensor RS for detecting a position of thegrinder G, and a guide mechanism 9 for allowing the grinder G to movesmoothly and vertically with keeping its posture.

As shown in FIGS. 10 and 11, the hanging member 5 is formed byconnecting a grinder mounting portion 50 and the partition plate 51 byfour connecting bars 52.

As shown in FIGS. 10 and 11, the retaining member 8 includes a thickupper plate 80, a thick lower plate 81, and four connecting bars 82which connect the upper and lower plates 80 and 81.

The upper and lower bellows cylinders 6 and 7 are formed by closingopposite end faces of bellows pipes with plate members. As shown inFIGS. 10 and 11, the upper bellows cylinder 6 is fixedly disposedbetween the upper plate 80 and the partition plate 51 and the lowerbellows cylinder 7 is between the partition plate 51 and the lower plate81. As shown in FIGS. 10 and 11, air from the compressor C can besupplied respectively to the upper bellows cylinder 6 through an airline 80a formed in the upper plate 80 and to the lower bellows cylinder7 through an air line 81 a formed in the lower plate 81. The upperbellows cylinder 6 may be formed by closing the opposite end faces ofthe bellows pipe with the upper plate 80 and the partition plate 51 andthe lower bellows cylinder 7 may be formed by closing the opposite endfaces of the bellows pipe with the partition plate 51 and the lowerplate 81.

As shown in FIG. 11, the linear sensor RS includes a main body RS1provided on a plate 83 hung across between the connecting bars 82 and82, and a rod RS2 provided on an upper face portion of the grindermounting portion 50 at its end portion. The position of the grinder Gcan be detected according to forward and backward movement of an inputshaft portion 51 due to vertical movement of the grinder G. In a statein which the grindstone g is pressed against an object W to be ground,in order to cancel elastic returning force of the upper and lowerbellows cylinders 6 and 7 generated when a position of the grinder G isshifted from a preset position, air pressure supplied to one of theupper and lower bellows cylinders 6 and 7 is changed by theelectro-pneumatic proportional valve in response to output informationof the linear sensor RS that has detected the position of the grinder G,thereby wear of the grindstone g or a slight displacement of the objectW to be ground being compensated.

As shown in FIGS. 10 and 11, the guide mechanism 9 includes a bearingportion 90 mounted on the partition plate 51 and a shaft portion 91 hungfrom the upper plate 80. The shaft portion 91 is closely and slidablyinserted into a bore in the bearing portion 90. Therefore, weight of thegrinder G produces moment on the partition plate 51. However, thepartition plate 51 moves vertically while maintaining a horizontal stateand the posture of the grinder G is not affected by the moment.

With the above structure of the grinder pressing device GK, the deviceGK has the following functions.

In order to move the grinder G upward, voltage or current to theelectro-pneumatic proportional valves K3 and K4 is changed so as to makethe internal pressure of the lower bellows cylinder 3 higher than thatof the upper bellows cylinder 6. In order to bring the grindstone g ofthe grinder G into contact with the object W to be ground, the voltageor the current to the electro-pneumatic proportional valve K3 is reducedso as to gradually lower the internal pressure of the lower bellowscylinder 7.

In the grinding process of the object W by the grindstone g of thegrinder G, a constant relationship between the internal pressures of theupper bellows cylinder 6 and the lower bellows cylinder 7 is maintainedto make the pressing force of the grindstone g to the object W to beground constant. In case the pressing force is made constant asdescribed above, regardless of wear of the grindstone g or a slightdisplacement of the object W to be ground, the pressing force applied tothe object W to be ground by the grindstone g is compensated by thelinear sensor RS and the like.

Furthermore, in this grinder pressing device GK, it is possible to knowthe position of the grinder G by the linear sensor RS and the like andto detect when to replace the grindstone g. Under the grinding processof the object W, an overload can be detected by the pressure sensors P1and P2. Moreover, the grinder pressing device GK in this Embodimentnecessitates no expensive device and enables very easy control, therebyresulting in a lower cost.

In this Embodiment, design modifications of the following (1) to (6) maybe made.

(1) In the above Embodiment, in the state in which the grindstone g ispressed against the object W to be ground, in order to cancel theelastic returning force of the upper and lower bellows cylinders 6 and 7generated when the position of the grinder G is shifted from the presetposition, air pressure supplied to one of the upper and lower bellowscylinders 6 and 7 is changed by the electro-pneumatic proportional valvein response to the output information of the linear sensor RS that hasdetected the position of the grinder G. However, such a system is notrequired in case elastic moduli of the upper and lower bellows cylinders6 and 7 are set to small values. This is because the elastic returningforce of the upper and lower bellows cylinders 6 and 7 generated whenthe position of the grinder G is shifted from the preset position areextremely small as compared with the pressing force of the grindstone gto the object W to be ground.

(2) In the above Embodiment, vertical movement of the grinder G andpressing force of the grindstone g to the object W to be ground are setby changing the internal pressures in the upper and lower bellowscylinders 6 and 7 by using the two electro-pneumatic proportional valvesK3 and K4. Alternatively, a system can be employed in which air pressurefed to one of the upper and lower bellows cylinders 6 and 7 is fixedwhile air pressure fed to the other is variable.

(3) In a system in which the object W to be ground is moved verticallyand the grindstone g is pressed against the object W, air pressuresrespectively fed to the upper and lower bellows cylinders 6 and 7 may befixed.

(4) The grinder G used for the system in the above Embodiment is an airtype grinder. However, this system may be applied to an electricgrinder.

(5) In the system of the above Embodiment, the grinder G m is, althoughnot limited thereto, attached to the fixed portion F, or the frame 99,through the grinder pressing device GK. Alternatively, for example, thegrinder G may be attached to an output portion of a robot through thegrinder pressing device GK.

INDUSTRIAL APPLICABILITY

As stated above, the grinder pressing device according to the presentinvention is, regardless of types of grinder, inexpensive and suitablefor grinding a portion where wear of the grindstone and the slightdisplacement of the object to be ground have to be compensated.

What is claimed is:
 1. A grinder pressing device comprising an aircylinder (1) in a vertical posture, a guide table (G2) and a guide (G1),wherein one of a bottom portion of a cylinder main body (10) and apiston rod (11) of said air cylinder (1) is fixed to a fixed plate (2)and other is mounted to a movable plate (3) disposed below said fixedplate (2), one of said guide table (G2) and said guide (G1) is mountedto a movable plate (3) side and other is mounted on an outer peripheralface of said cylinder main body (10), said guide table (G2) is guided onsaid guide (G1) in a vertical direction under a rolling frictionalcondition through balls (B), said air cylinder (1) is formed in a mannerthat hermeticity is provided by metal seals (MS) between outerperipheral walls of a piston (12) and said piston rod (11) and astructural wall of said cylinder main body (10) side so as to setfriction coefficients between said walls low and that said piston rod(11) is supported by a ball bushing (BS) in a large area to move forwardand backward, said movable plate (3) is provided directly or throughanother member with a grinder (G), and pressing force applied to anobject to be ground by said grinder (G) can be controlled by adjustingair pressure of upper and lower cylinder chambers (13, 14) separated bysaid piston (12).
 2. A grinder pressing device according to claim 1,wherein a linear sensor (RS) for detecting a position of said movableplate (3) with respect to said fixed plate (2) is provided so as todetect a position of said grinder (G).
 3. A grinder pressing deviceaccording to claim 2, wherein a main body (RS1) side of said linearsensor (RS) is mounted on said cylinder main body (10) and a shaftportion (RS2) of said linear sensor (RS) is mounted on said movableplate (3).
 4. A grinder pressing device according to claim 1, wherein adust-proof bellows pipe (4) for surrounding a part and a member disposedbetween said fixed plate (2) and said movable plate (3) is provided andexpansion-contraction resistance of said bellows pipe (4) is set verysmall.
 5. A grinder pressing device comprising a hanging member (5)having a grinder mounting portion (50) and a partition plate (51), upperand lower bellows cylinders (6) (7) fixedly disposed on upper and lowerfaces of said partition plate (51), and a retaining member (8) formaintaining a constant distance between an upper face of said upperbellows cylinder (6) and a lower face of said lower bellows cylinder(7), wherein said retaining member (8) is mounted to one of a fixedportion (F) and a robot output portion, said grinder mounting portion(50) is provided with a grinder (G), and said upper and lower bellowscylinders (6)(7) are supplied with air of respectively predeterminedpressures.
 6. A grinder pressing device according to claim 5, whereinsaid upper and lower bellows cylinders (6)(7) are respectively suppliedwith air so as to cause lifting force to act on said partition plate(51) of said hanging member (5).
 7. A grinder pressing device accordingto claim 5 , wherein at least one of air pressures supplied respectivelyto said upper and lower bellows cylinders (6)(7) is changeable.
 8. Agrinder pressing device according to claim 5, wherein at least one ofair pressures supplied to said upper and lower bellows cylinders (6)(7)is changeable in response to output information of a linear sensor (RS)for detecting a position of said grinder (G) so as to cancel elasticreturning force of said upper and lower bellows cylinders (6)(7)generated when said position of said grinder (G) in a state in which agrindstone (g) is pressed against an object (W) to be ground is shiftedfrom a predetermined position.
 9. A grinder pressing device according toclaim 7, wherein at least one of air pressures supplied to said upperand lower bellows cylinders (6)(7) is changeable in response to outputinformation of a linear sensor (RS) for detecting a position of saidgrinder (G) so as to cancel elastic returning force of said upper andlower bellows cylinders (6)(7) generated when a position of said grinder(G) in a state in which a grindstone (g) is pressed against an object(W) to be ground is shifted from a predetermined position.
 10. A grinderpressing device according to claim 8, wherein when said linear sensor(RS) outputs information that a position of said grinder (G) is shiftedmore than a certain amount from said predetermined position, a warningmeans is put into an output state or said grinder (G) is set to stop.11. A grinder pressing device according to claim 9, wherein when saidlinear sensor (RS) outputs information that a position of said grinder(G) is shifted more than a certain amount from said predeterminedposition, a warning means is put into an output state or said grinder(G) is set to stop.
 12. A grinder pressing device according to claim 5,wherein said upper and lower bellows cylinders (6)(7) have a samediameter and are disposed on a same vertical axis.
 13. A grinderpressing device according to claim 7, wherein said upper and lowerbellows cylinders (6)(7) have a same diameter and are disposed on a samevertical axis.
 14. A grinder pressing device according to claim 8,wherein said upper and lower bellows cylinders (6)(7) have a samediameter and are disposed on a same vertical axis.
 15. A grinderpressing device according to claim 9, wherein said upper and lowerbellows cylinders (6)(7) have a same diameter and are disposed on a samevertical axis.
 16. A grinder pressing device according to claim 10,wherein said upper and lower bellows cylinders (6)(7) have a samediameter and are disposed on a same vertical axis.
 17. A grinderpressing device according to claim 11, wherein said upper and lowerbellows cylinders (6)(7) have a same diameter and are disposed on a samevertical axis.